Chủ nhà ở tầng một.

Literally, chủ nhà means the owner/master of the house:

• chủ = owner, person in charge
• nhà = house, home

In real usage, chủ nhà can mean different things depending on context:

• homeowner
• landlord / landlady
• sometimes host / hostess

So the exact English word depends on the situation, even though the Vietnamese phrase stays the same.

Ở is a very common word meaning to be at, to stay at, or to live in/on/at a place.

In this sentence, it links the person to a location:

• chủ nhà = the owner / landlord
• ở = is at / lives at
• tầng một = first floor / floor one

So ở is doing the job of expressing location. Depending on context, the sentence can sound like either:

• the owner is on that floor
• the owner lives on that floor

The pattern is:

Subject + ở + location

So here:

• Chủ nhà = subject
• ở = location verb
• tầng một = place/location

This is a very common Vietnamese structure. English often needs extra words like on, in, or at, but Vietnamese often uses ở plus the place phrase.

Because Vietnamese does not always match English prepositions one-for-one.

In English, you say:

• on the first floor

But in Vietnamese, ở already sets up the location, and tầng một is understood as the place. So Vietnamese does not need a separate word exactly equivalent to English on here.

That is why ở tầng một sounds natural.

Literally, tầng một means floor one.

But the real-world meaning can vary depending on local building conventions:

• In some contexts, tầng trệt is the ground floor, so tầng một is the floor above it.
• In other contexts, especially on signs, tầng 1 may refer to the ground-level floor.

So an English speaker should be careful: floor numbering does not always line up perfectly with British or American usage.

Because Vietnamese normally numbers floors with cardinal numbers, not with a form meaning first in the English sense.

So you get:

• tầng một = floor one
• tầng hai = floor two
• tầng ba = floor three

Nhất is not what you normally use for numbering floors in everyday Vietnamese.

Vietnamese does not have articles that work like English a / an / the.

So chủ nhà can be understood as:

• the landlord
• a landlord
• the owner

Which one sounds best depends on context. Vietnamese leaves that information unstated unless there is a reason to make it explicit.

No. Chủ nhà does not show gender.

If you need to make that clear, Vietnamese can add a gendered word, for example:

• ông chủ nhà = male owner / landlord
• bà chủ nhà = female owner / landlady

But in the original sentence, gender is simply not specified.

Yes. That would be natural too.

• ở tầng một = is / stays / lives on the first floor
• sống ở tầng một = lives on the first floor

Using sống makes the meaning more clearly about living there, while ở is broader and can describe either residence or current location, depending on context.

A rough pronunciation guide is:

• chủ ≈ choo (with a dipping tone)
• nhà ≈ nya (with a low falling tone)
• ở ≈ a short vowel like uh/er (with a dipping tone)
• tầng ≈ tuhng / tung with ng at the end
• một ≈ moht with a short, clipped ending

A few important points:

• nh in nhà sounds like ny in canyon
• tầng ends with -ng
• một ends with a final t that is not strongly released
• the tones matter a lot, especially on chủ, ở, and nhà

So it is better to learn it from audio if possible, not only from English-style spelling.